The earliest significant efforts to restrict immigration to the U.S. came in the late 1800s, when inspection stations were set up at ports of entry along the southern border. But controls began to ease because of labor shortages during World War I. The U.S. Border Patrol began in 1924, as Prohibition encouraged a brisk smuggling trade from Mexico into the U.S. The first mass deportations of Mexicans came during the Great Depression, which lasted from 1929 until the start of the Second World War. During the Depression,
American migrants poured into California from Oklahoma and other "dust bowl" states, desperate for work in the fields or anywhere they could find it.

The Braceros, Operation Wetback and Quotas1942-1965

Fighting on two fronts in Europe and Asia during the war, the United States looked to Mexico to help keep America fed and its railroad running. A guest-worker treaty, known as the Bracero Program, started in August 1942 with a few hundred Mexican farm workers. By 1964, when the program ended because of floods of illegal migrants, improved farming techniques and reports that workers had been mistreated, more than 4.5 million Mexicans had participated. Illegal immigration increased after the war ended, as the guest-worker program slowed and Mexicans still came for jobs. The response by the U.S. government in 1954 was to launch Operation Wetback, in which nearly 4 million Mexican immigrants were deported back to Mexico. While the Mexican government pushed economic growth and the country’s population grew by 10 million through the 1960s (from 38 million to 48 million by the end of the decade), political and social unrest rose, as evidenced by demonstrations at the1968 Summer Olympics in Mexico City.

The first maquiladoras, or assembly plants, were built in Mexican border towns to provide cheap labor and goods for U.S. companies as the Bracero program ended.

In 1965, Congress passed the Immigration and Nationality Act, which ended numerical restrictions by country of origin on immigrants allowed to enter the United States. (Instead, the act capped the number of immigrants permitted to emigrate by Eastern and Western hemisphere.) Pushed by President John F. Kennedy and signed by Lyndon Johnson, the new immigration policy aimed to portray the U.S. in a better light against the rise of communism and to promote American ideals. Meanwhile, Mexico experienced a strong post-war boom, but most of the nation’s wealth remained concentrated among the wealthiest residents.

Illegal Immigration Deemed Out of Control1970s

By the start of the 1970s, the number of illegal aliens had tripled since 1965, and four out of five illegal immigrants arriving to the U.S. are from Mexico. By 1972, the now-defunct Immigration and Naturalization Service estimated that the illegal immigrant population had topped 1 million, leading many to call illegal immigration out of control. For the rest of the decade, the estimates of the country's illegal immigrant population varied widely. In 1975, the U.S. House of Representatives introduced a bill providing for amnesty along with employer sanctions for hiring illegal immigrants. Concerned about the rise in illegal immigration, President Gerald Ford set up a Domestic Council Committee on Illegal Aliens, which reported that illegal immigrants were driving down the wages of low-skilled workers. The committee findings urged employer sanctions, harsher penalties for smugglers and an amnesty program. Congress was dissatisfied with the proposals, and in 1978 passed a law to create the Select Commission on Immigration and Refugee Policy to further explore national solutions. Under the Carter administration, the Select Commission determined that the nation’s immigration policy was in disarray. The Select Commission recommended a focus on law enforcement, such as employer sanctions for hiring illegal immigrants, and better border security. It simultaneously rejected a foreign guest-worker program, while supporting amnesty for illegal immigrants. Little action was taken immediately.

Meanwhile, Mexico's nationalized oil industry boomed with the discovery, in 1976, of a huge offshore oil reserve called the Cantarell Field. But by the end of the decade, the government’s fiscal mismanagement had left the country deep in debt, and even basic food production faltered. The economy ricocheted between boom and bust into the early 1980s.

Recession, Amnesty and the Right to Education
1980s

At the beginning of the 1980s, Mexico’s economy was teetering, shaken by the nation's worst recession since the 1930s. In 1982, the peso was devalued repeatedly during the country’s economic crisis. High unemployment pushed more migrants to find work in the United States. That same year, the U.S. Supreme Court ruled that children who were illegal residents had the right to public school education. Maquiladoras continued to expand along the border towns, assembling goods for the U.S. market.

In 1986, Congress passed more legislation with the Immigration Reform and Control Act, aimed at stemming the flow of illegal immigration by cracking down on U.S. employers who hire illegal immigrants. The act also granted an amnesty to illegal workers already in the United States, giving more than 2.7 million people legal status.

By the mid-1980s, the total alien population was estimated to be nearly 5 million, and in 1986, the border patrol reported a record 1.7 million apprehensions of illegal Mexican immigrants. As a result of the amnesty, illegal immigration plummeted over the next two years before rebounding at the beginning of the 1990s. The annual budget for the Immigration and Naturalization Service (INS) increased nearly fourfold from the previous decade to more than $800 million in 1988. Mexican President Carlos Salinas de Gortari, who was elected in 1988 on a reform platform, pushed to privatize the nation’s nationalized industry and deregulate the economy, paving the way for the North American Free Trade Agreement, or NAFTA.

Immigration Reform 1990s

During the 1990s, immigration was again at the forefront of the political reform agenda, starting with the Immigration Act of 1990 under President George H. W. Bush. Drawing from recommendations by the Select Commission a decade before, the new law not only increased the number of legal immigrants allowed into the U.S. each year, from 500,000 to 700,000, but it also created a visa lottery system to promote "diversity" from underrepresented countries, such as some African nations. The law also initiated the U.S. Commission on Immigration Reform, which recommended that the government focus on improving border enforcement through more training for border officials. The reform also cracked down on employers hiring illegal workers and eliminated non-emergency medical services for illegal immigrants. Meanwhile, the number of illegal immigrants, which had dropped following the amnesty of 1986, climbed back to an estimated 3.4 million in 1992.

The Effects of NAFTA1990s

The North American Free Trade Agreement, ratified under President Bill Clinton, went into effect in 1994, to eliminate tariffs over 15 years and to turn the United States, Mexico and Canada into the world’s second largest trading bloc after the European Union. Critics believed that the trade agreement would undercut Mexican farmers with cheap U.S. food imports and exacerbate inequality between the two countries. A flagging Mexican economy received an initial boost from foreign investment related to NAFTA. But an economic crisis -- caused in part by political instability, a drop in foreign investor confidence, and a government spending spree toward the end of Salinas’ presidency, among other factors -- befell the country and the peso collapsed in late 1994. Despite privatization and NAFTA, wealth still remained mostly concentrated within the elite classes, and the wage gap between Mexico and the United States remained wide.

Although some economists agree that NAFTA has stimulated a rise in real income for Mexicans, the country as a whole continues to lack the infrastructure in agribusiness and other industries, and the investment in education and innovation to become more competitive with its northern neighbor.

Tightening the Border1990s

In El Paso, Texas, one of the two main corridors for illegal entry (the other being San Diego), the Border Patrol began a new program to clamp down on illegal immigration. Sector Chief Silvestre Reyes, now a Democratic Congressman, launched Operation Blockade, which roughly doubled the number of border agents patrolling the area between Ciudad Juarez and El Paso around the clock. Originally scheduled to last two weeks, the operation was expanded and renamed Operation Hold the Line; as a result, apprehensions of illegal immigrants dropped significantly in the area.

A report by Sandia National Laboratory determined that the INS strategy of tracking down and apprehending illegal immigrants was ineffective, which led the Border Patrol to revamp its national strategy in 1994. (In 1993, the annual budget of the INS had climbed to $1.5 billion.) Borrowing from Reyes’ Operation Hold the Line, the new focus was to prevent illegal immigration through deterrence. This called for more fencing, border patrol agents, technology, lighting and surveillance equipment to be implemented in four phases.

The phase included El Paso's Hold the Line and San Diego's Operation Gatekeeper, which targeted the busiest illegal crossing point in the southwest. The goal was to push migrants into more remote and difficult locations to dissuade them from crossing. The Clinton administration unveiled an immigration law enforcement plan in February 1994 that prioritized increasing border security, deporting criminal aliens, reorganizing the asylum process, ensuring greater enforcement in the workplace and encouraging legal immigrants to seek citizenship.

In 1996, Congress passed legislation mandating jail time for some criminal aliens and authorizing the hiring of more Border Patrol agents over the next several years. Deportees could now also be held in jail for up to two years before appearing before an immigration board. And power was given to local law enforcement in the border states to deputize police forces to uphold immigration laws.

The strategy of pushing more immigrants into the desert and away from the major San Diego and El Paso smuggling routes was deemed a success in 1998, as the flow of illegal immigrants moved into more remote areas. An unintended consequence of this was to increase the number of deaths of migrants trying to traverse the scorching desert.

9/11 and Homeland Security 2000 to Present

As the 21st century approached, the number of illegal immigrants apprehended reached 1.6 million in 2000, and INS estimated that there were 7 million illegal immigrants living in the United States in 2000 -- more than half of whom were Mexican. Other estimates pegged the number of illegal immigrants at more than 9 million. INS was operating with a budget of $5 billion, three times that of a decade ago, and by the end of 2000, the maquiladoras were in decline, challenged by cheaper labor in Asia and elsewhere. Mexico’s economy suffered a recession along with United States.

The 9/11 terrorist attack in 2001 intensified security at the border, with an emphasis on preventing terrorists from entering the country. In response to the attacks, the Department of Homeland Security (DHS) was set up in 2003, swallowing the INS, Customs and the United States Department of Agriculture (USDA); DHS reorganized the former agencies into Customs and Border Protection, Immigration and Customs Enforcement and Citizenship and Immigration Services, along with nearly 20 other agencies. The same year, the money flooding back to Mexico from migrants in the U.S. surpassed $10 billion for the first time. President Bush proposed a guest-worker program that was met with strong opposition in Congress and complaints that it would lead to another amnesty.

The Border Patrol continued to grow as more emphasis was put on securing the U.S. border in the wake of 9/11. Congress increased spending and passed new laws, including the Intelligence Reform and Terrorism Prevention Act in 2004, which authorized adding 10,000 new agents. These agents are expected to nearly double the Border Patrol force from 11,000 to 21,000 by 2010.

In the last few years, Congress has attempted to pass comprehensive immigration reform bills in both the House and Senate. The efforts ultimately stalled because Congress could not reach a consensus. House Republicans, such as Representative James Sensenbrenner (R-WI), demanded greater border security, including the construction of more fencing, while a broader bipartisan Senate reform bill, known as McCain-Kennedy, called for enhanced security along with a guest-worker program and a path toward citizenship. Since taking office in 2006, Mexican President Felipe Calderon has sent thousands of troops to the U.S.-Mexico border to combat drug traffickers. In the fall of 2006, President Bush signed the Secure Fence Act, calling for roughly 700 miles of border fencing.

While Mexico's Congress voted to decriminalize illegal immigration in its country in spring 2008, the U.S. ramped up Operation Streamline in an effort to prosecute more illegal border crossings. In April 2008, the U.S. Justice Department announced it would spend $7 million to send more than 60 more prosecutors to border districts to prosecute border crimes, such as human smuggling.